The goal is to test the hypothesis that genetic vaccines encoding human ErbB-2 fused to an adjuvant sequence will induce effective anti-tumor immunity in ErbB-2 tolerant hosts. A panel of DNA constructs encoding tyrosine kinase free ErbB-2 fragments to activate selected anti-ErbB-2 response have demonstrated striking anti-tumor activity in BALB/c and C57BL/6 mice. To further enhance the immunogenicity, ErbB-2 DNA will be fused to a sequence encoding the immunogenic domain 1 of Tetanus Toxin Fragment C (tetl) and tested by electrovaccination. The mechanism and efficacy of DNA vaccine will be compared side-byside with dendritic cells transfected with mRNA of the same antigen sequence. Prevention or therapy of ErbB-2 positive tumors will be tested in human ErbB-2 and rat neu transgenic mice. Spontaneous tumors from neu transgenic mice and tumor cells transfected with ErbB-2 represent antibody sensitive and resistant tumors, respectively. The mechanism of TR cells in controlling anti-ErbB-2 immunity will be determined and vaccination efficacy in TR cells depleted mice will be tested. Following results from these studies, a comprehensive vaccination scheme will be tested with selected agents. Therefore, mice will be pre-sensitized with Tetanus toxoid. TR cells will be removed and mice will be immunized with a 1st line vaccine which induces both humoral and cellular responses until functional antibody is achieved, then boosted with a vaccine which activates T cells only. Epitope spreading induced during immune rejection of ErbB-2 positive tumors will be characterized to indicate additional efficacy. Cancer therapeutic agents which induce ErbB-2 protein degradation to increase ErbB-2 presentation to CTL, including anti-ErbB-2 mAb and 17-allyl-aminogledanamycin (17-AAG) will be tested as CTL enhancing agents. Specifically, we will (1) further developand characterize human ErbB-2 DNA and dendritic cell vaccines, (2) analyze anti-ErbB-2 immunity in tumor prevention and therapy, suppress negative immune regulators, enhance epitope spreading, and (3) test the efficacy of combining ErbB-2 modulating agents with active vaccination. By developing this comprehensive vaccination and therapy scheme, long-term tumor-free survival can be expected.